Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1 | /* |
| 2 | * fs/userfaultfd.c |
| 3 | * |
| 4 | * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> |
| 5 | * Copyright (C) 2008-2009 Red Hat, Inc. |
| 6 | * Copyright (C) 2015 Red Hat, Inc. |
| 7 | * |
| 8 | * This work is licensed under the terms of the GNU GPL, version 2. See |
| 9 | * the COPYING file in the top-level directory. |
| 10 | * |
| 11 | * Some part derived from fs/eventfd.c (anon inode setup) and |
| 12 | * mm/ksm.c (mm hashing). |
| 13 | */ |
| 14 | |
| 15 | #include <linux/hashtable.h> |
| 16 | #include <linux/sched.h> |
| 17 | #include <linux/mm.h> |
| 18 | #include <linux/poll.h> |
| 19 | #include <linux/slab.h> |
| 20 | #include <linux/seq_file.h> |
| 21 | #include <linux/file.h> |
| 22 | #include <linux/bug.h> |
| 23 | #include <linux/anon_inodes.h> |
| 24 | #include <linux/syscalls.h> |
| 25 | #include <linux/userfaultfd_k.h> |
| 26 | #include <linux/mempolicy.h> |
| 27 | #include <linux/ioctl.h> |
| 28 | #include <linux/security.h> |
| 29 | |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 30 | static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly; |
| 31 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 32 | enum userfaultfd_state { |
| 33 | UFFD_STATE_WAIT_API, |
| 34 | UFFD_STATE_RUNNING, |
| 35 | }; |
| 36 | |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 37 | /* |
| 38 | * Start with fault_pending_wqh and fault_wqh so they're more likely |
| 39 | * to be in the same cacheline. |
| 40 | */ |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 41 | struct userfaultfd_ctx { |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 42 | /* waitqueue head for the pending (i.e. not read) userfaults */ |
| 43 | wait_queue_head_t fault_pending_wqh; |
| 44 | /* waitqueue head for the userfaults */ |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 45 | wait_queue_head_t fault_wqh; |
| 46 | /* waitqueue head for the pseudo fd to wakeup poll/read */ |
| 47 | wait_queue_head_t fd_wqh; |
Andrea Arcangeli | 2c5b7e1 | 2015-09-04 15:47:23 -0700 | [diff] [blame] | 48 | /* a refile sequence protected by fault_pending_wqh lock */ |
| 49 | struct seqcount refile_seq; |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 50 | /* pseudo fd refcounting */ |
| 51 | atomic_t refcount; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 52 | /* userfaultfd syscall flags */ |
| 53 | unsigned int flags; |
| 54 | /* state machine */ |
| 55 | enum userfaultfd_state state; |
| 56 | /* released */ |
| 57 | bool released; |
| 58 | /* mm with one ore more vmas attached to this userfaultfd_ctx */ |
| 59 | struct mm_struct *mm; |
| 60 | }; |
| 61 | |
| 62 | struct userfaultfd_wait_queue { |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 63 | struct uffd_msg msg; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 64 | wait_queue_t wq; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 65 | struct userfaultfd_ctx *ctx; |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 66 | bool waken; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 67 | }; |
| 68 | |
| 69 | struct userfaultfd_wake_range { |
| 70 | unsigned long start; |
| 71 | unsigned long len; |
| 72 | }; |
| 73 | |
| 74 | static int userfaultfd_wake_function(wait_queue_t *wq, unsigned mode, |
| 75 | int wake_flags, void *key) |
| 76 | { |
| 77 | struct userfaultfd_wake_range *range = key; |
| 78 | int ret; |
| 79 | struct userfaultfd_wait_queue *uwq; |
| 80 | unsigned long start, len; |
| 81 | |
| 82 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
| 83 | ret = 0; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 84 | /* len == 0 means wake all */ |
| 85 | start = range->start; |
| 86 | len = range->len; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 87 | if (len && (start > uwq->msg.arg.pagefault.address || |
| 88 | start + len <= uwq->msg.arg.pagefault.address)) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 89 | goto out; |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 90 | WRITE_ONCE(uwq->waken, true); |
| 91 | /* |
| 92 | * The implicit smp_mb__before_spinlock in try_to_wake_up() |
| 93 | * renders uwq->waken visible to other CPUs before the task is |
| 94 | * waken. |
| 95 | */ |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 96 | ret = wake_up_state(wq->private, mode); |
| 97 | if (ret) |
| 98 | /* |
| 99 | * Wake only once, autoremove behavior. |
| 100 | * |
| 101 | * After the effect of list_del_init is visible to the |
| 102 | * other CPUs, the waitqueue may disappear from under |
| 103 | * us, see the !list_empty_careful() in |
| 104 | * handle_userfault(). try_to_wake_up() has an |
| 105 | * implicit smp_mb__before_spinlock, and the |
| 106 | * wq->private is read before calling the extern |
| 107 | * function "wake_up_state" (which in turns calls |
| 108 | * try_to_wake_up). While the spin_lock;spin_unlock; |
| 109 | * wouldn't be enough, the smp_mb__before_spinlock is |
| 110 | * enough to avoid an explicit smp_mb() here. |
| 111 | */ |
| 112 | list_del_init(&wq->task_list); |
| 113 | out: |
| 114 | return ret; |
| 115 | } |
| 116 | |
| 117 | /** |
| 118 | * userfaultfd_ctx_get - Acquires a reference to the internal userfaultfd |
| 119 | * context. |
| 120 | * @ctx: [in] Pointer to the userfaultfd context. |
| 121 | * |
| 122 | * Returns: In case of success, returns not zero. |
| 123 | */ |
| 124 | static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx) |
| 125 | { |
| 126 | if (!atomic_inc_not_zero(&ctx->refcount)) |
| 127 | BUG(); |
| 128 | } |
| 129 | |
| 130 | /** |
| 131 | * userfaultfd_ctx_put - Releases a reference to the internal userfaultfd |
| 132 | * context. |
| 133 | * @ctx: [in] Pointer to userfaultfd context. |
| 134 | * |
| 135 | * The userfaultfd context reference must have been previously acquired either |
| 136 | * with userfaultfd_ctx_get() or userfaultfd_ctx_fdget(). |
| 137 | */ |
| 138 | static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx) |
| 139 | { |
| 140 | if (atomic_dec_and_test(&ctx->refcount)) { |
| 141 | VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock)); |
| 142 | VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh)); |
| 143 | VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock)); |
| 144 | VM_BUG_ON(waitqueue_active(&ctx->fault_wqh)); |
| 145 | VM_BUG_ON(spin_is_locked(&ctx->fd_wqh.lock)); |
| 146 | VM_BUG_ON(waitqueue_active(&ctx->fd_wqh)); |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 147 | mmdrop(ctx->mm); |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 148 | kmem_cache_free(userfaultfd_ctx_cachep, ctx); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 149 | } |
| 150 | } |
| 151 | |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 152 | static inline void msg_init(struct uffd_msg *msg) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 153 | { |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 154 | BUILD_BUG_ON(sizeof(struct uffd_msg) != 32); |
| 155 | /* |
| 156 | * Must use memset to zero out the paddings or kernel data is |
| 157 | * leaked to userland. |
| 158 | */ |
| 159 | memset(msg, 0, sizeof(struct uffd_msg)); |
| 160 | } |
| 161 | |
| 162 | static inline struct uffd_msg userfault_msg(unsigned long address, |
| 163 | unsigned int flags, |
| 164 | unsigned long reason) |
| 165 | { |
| 166 | struct uffd_msg msg; |
| 167 | msg_init(&msg); |
| 168 | msg.event = UFFD_EVENT_PAGEFAULT; |
| 169 | msg.arg.pagefault.address = address; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 170 | if (flags & FAULT_FLAG_WRITE) |
| 171 | /* |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 172 | * If UFFD_FEATURE_PAGEFAULT_FLAG_WRITE was set in the |
| 173 | * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WRITE |
| 174 | * was not set in a UFFD_EVENT_PAGEFAULT, it means it |
| 175 | * was a read fault, otherwise if set it means it's |
| 176 | * a write fault. |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 177 | */ |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 178 | msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 179 | if (reason & VM_UFFD_WP) |
| 180 | /* |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 181 | * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the |
| 182 | * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WP was |
| 183 | * not set in a UFFD_EVENT_PAGEFAULT, it means it was |
| 184 | * a missing fault, otherwise if set it means it's a |
| 185 | * write protect fault. |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 186 | */ |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 187 | msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP; |
| 188 | return msg; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 189 | } |
| 190 | |
| 191 | /* |
Andrea Arcangeli | 8d2afd9 | 2015-09-04 15:46:51 -0700 | [diff] [blame] | 192 | * Verify the pagetables are still not ok after having reigstered into |
| 193 | * the fault_pending_wqh to avoid userland having to UFFDIO_WAKE any |
| 194 | * userfault that has already been resolved, if userfaultfd_read and |
| 195 | * UFFDIO_COPY|ZEROPAGE are being run simultaneously on two different |
| 196 | * threads. |
| 197 | */ |
| 198 | static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx, |
| 199 | unsigned long address, |
| 200 | unsigned long flags, |
| 201 | unsigned long reason) |
| 202 | { |
| 203 | struct mm_struct *mm = ctx->mm; |
| 204 | pgd_t *pgd; |
| 205 | pud_t *pud; |
| 206 | pmd_t *pmd, _pmd; |
| 207 | pte_t *pte; |
| 208 | bool ret = true; |
| 209 | |
| 210 | VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem)); |
| 211 | |
| 212 | pgd = pgd_offset(mm, address); |
| 213 | if (!pgd_present(*pgd)) |
| 214 | goto out; |
| 215 | pud = pud_offset(pgd, address); |
| 216 | if (!pud_present(*pud)) |
| 217 | goto out; |
| 218 | pmd = pmd_offset(pud, address); |
| 219 | /* |
| 220 | * READ_ONCE must function as a barrier with narrower scope |
| 221 | * and it must be equivalent to: |
| 222 | * _pmd = *pmd; barrier(); |
| 223 | * |
| 224 | * This is to deal with the instability (as in |
| 225 | * pmd_trans_unstable) of the pmd. |
| 226 | */ |
| 227 | _pmd = READ_ONCE(*pmd); |
| 228 | if (!pmd_present(_pmd)) |
| 229 | goto out; |
| 230 | |
| 231 | ret = false; |
| 232 | if (pmd_trans_huge(_pmd)) |
| 233 | goto out; |
| 234 | |
| 235 | /* |
| 236 | * the pmd is stable (as in !pmd_trans_unstable) so we can re-read it |
| 237 | * and use the standard pte_offset_map() instead of parsing _pmd. |
| 238 | */ |
| 239 | pte = pte_offset_map(pmd, address); |
| 240 | /* |
| 241 | * Lockless access: we're in a wait_event so it's ok if it |
| 242 | * changes under us. |
| 243 | */ |
| 244 | if (pte_none(*pte)) |
| 245 | ret = true; |
| 246 | pte_unmap(pte); |
| 247 | |
| 248 | out: |
| 249 | return ret; |
| 250 | } |
| 251 | |
| 252 | /* |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 253 | * The locking rules involved in returning VM_FAULT_RETRY depending on |
| 254 | * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NOWAIT and |
| 255 | * FAULT_FLAG_KILLABLE are not straightforward. The "Caution" |
| 256 | * recommendation in __lock_page_or_retry is not an understatement. |
| 257 | * |
| 258 | * If FAULT_FLAG_ALLOW_RETRY is set, the mmap_sem must be released |
| 259 | * before returning VM_FAULT_RETRY only if FAULT_FLAG_RETRY_NOWAIT is |
| 260 | * not set. |
| 261 | * |
| 262 | * If FAULT_FLAG_ALLOW_RETRY is set but FAULT_FLAG_KILLABLE is not |
| 263 | * set, VM_FAULT_RETRY can still be returned if and only if there are |
| 264 | * fatal_signal_pending()s, and the mmap_sem must be released before |
| 265 | * returning it. |
| 266 | */ |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 267 | int handle_userfault(struct vm_fault *vmf, unsigned long reason) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 268 | { |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 269 | struct mm_struct *mm = vmf->vma->vm_mm; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 270 | struct userfaultfd_ctx *ctx; |
| 271 | struct userfaultfd_wait_queue uwq; |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 272 | int ret; |
Andrea Arcangeli | dfa37dc | 2015-09-04 15:47:18 -0700 | [diff] [blame] | 273 | bool must_wait, return_to_userland; |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 274 | long blocking_state; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 275 | |
| 276 | BUG_ON(!rwsem_is_locked(&mm->mmap_sem)); |
| 277 | |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 278 | ret = VM_FAULT_SIGBUS; |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 279 | ctx = vmf->vma->vm_userfaultfd_ctx.ctx; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 280 | if (!ctx) |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 281 | goto out; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 282 | |
| 283 | BUG_ON(ctx->mm != mm); |
| 284 | |
| 285 | VM_BUG_ON(reason & ~(VM_UFFD_MISSING|VM_UFFD_WP)); |
| 286 | VM_BUG_ON(!(reason & VM_UFFD_MISSING) ^ !!(reason & VM_UFFD_WP)); |
| 287 | |
| 288 | /* |
| 289 | * If it's already released don't get it. This avoids to loop |
| 290 | * in __get_user_pages if userfaultfd_release waits on the |
| 291 | * caller of handle_userfault to release the mmap_sem. |
| 292 | */ |
| 293 | if (unlikely(ACCESS_ONCE(ctx->released))) |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 294 | goto out; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 295 | |
| 296 | /* |
Linus Torvalds | 39680f5 | 2016-03-01 11:56:22 -0800 | [diff] [blame] | 297 | * We don't do userfault handling for the final child pid update. |
| 298 | */ |
| 299 | if (current->flags & PF_EXITING) |
| 300 | goto out; |
| 301 | |
| 302 | /* |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 303 | * Check that we can return VM_FAULT_RETRY. |
| 304 | * |
| 305 | * NOTE: it should become possible to return VM_FAULT_RETRY |
| 306 | * even if FAULT_FLAG_TRIED is set without leading to gup() |
| 307 | * -EBUSY failures, if the userfaultfd is to be extended for |
| 308 | * VM_UFFD_WP tracking and we intend to arm the userfault |
| 309 | * without first stopping userland access to the memory. For |
| 310 | * VM_UFFD_MISSING userfaults this is enough for now. |
| 311 | */ |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 312 | if (unlikely(!(vmf->flags & FAULT_FLAG_ALLOW_RETRY))) { |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 313 | /* |
| 314 | * Validate the invariant that nowait must allow retry |
| 315 | * to be sure not to return SIGBUS erroneously on |
| 316 | * nowait invocations. |
| 317 | */ |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 318 | BUG_ON(vmf->flags & FAULT_FLAG_RETRY_NOWAIT); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 319 | #ifdef CONFIG_DEBUG_VM |
| 320 | if (printk_ratelimit()) { |
| 321 | printk(KERN_WARNING |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 322 | "FAULT_FLAG_ALLOW_RETRY missing %x\n", |
| 323 | vmf->flags); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 324 | dump_stack(); |
| 325 | } |
| 326 | #endif |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 327 | goto out; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 328 | } |
| 329 | |
| 330 | /* |
| 331 | * Handle nowait, not much to do other than tell it to retry |
| 332 | * and wait. |
| 333 | */ |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 334 | ret = VM_FAULT_RETRY; |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 335 | if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 336 | goto out; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 337 | |
| 338 | /* take the reference before dropping the mmap_sem */ |
| 339 | userfaultfd_ctx_get(ctx); |
| 340 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 341 | init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function); |
| 342 | uwq.wq.private = current; |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 343 | uwq.msg = userfault_msg(vmf->address, vmf->flags, reason); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 344 | uwq.ctx = ctx; |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 345 | uwq.waken = false; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 346 | |
Kirill A. Shutemov | bae473a | 2016-07-26 15:25:20 -0700 | [diff] [blame] | 347 | return_to_userland = |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 348 | (vmf->flags & (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE)) == |
Andrea Arcangeli | dfa37dc | 2015-09-04 15:47:18 -0700 | [diff] [blame] | 349 | (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE); |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 350 | blocking_state = return_to_userland ? TASK_INTERRUPTIBLE : |
| 351 | TASK_KILLABLE; |
Andrea Arcangeli | dfa37dc | 2015-09-04 15:47:18 -0700 | [diff] [blame] | 352 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 353 | spin_lock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 354 | /* |
| 355 | * After the __add_wait_queue the uwq is visible to userland |
| 356 | * through poll/read(). |
| 357 | */ |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 358 | __add_wait_queue(&ctx->fault_pending_wqh, &uwq.wq); |
| 359 | /* |
| 360 | * The smp_mb() after __set_current_state prevents the reads |
| 361 | * following the spin_unlock to happen before the list_add in |
| 362 | * __add_wait_queue. |
| 363 | */ |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 364 | set_current_state(blocking_state); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 365 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 366 | |
Jan Kara | 82b0f8c | 2016-12-14 15:06:58 -0800 | [diff] [blame] | 367 | must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags, |
| 368 | reason); |
Andrea Arcangeli | 8d2afd9 | 2015-09-04 15:46:51 -0700 | [diff] [blame] | 369 | up_read(&mm->mmap_sem); |
| 370 | |
| 371 | if (likely(must_wait && !ACCESS_ONCE(ctx->released) && |
Andrea Arcangeli | dfa37dc | 2015-09-04 15:47:18 -0700 | [diff] [blame] | 372 | (return_to_userland ? !signal_pending(current) : |
| 373 | !fatal_signal_pending(current)))) { |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 374 | wake_up_poll(&ctx->fd_wqh, POLLIN); |
| 375 | schedule(); |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 376 | ret |= VM_FAULT_MAJOR; |
Andrea Arcangeli | 15a77c6 | 2017-01-24 15:17:59 -0800 | [diff] [blame] | 377 | |
| 378 | /* |
| 379 | * False wakeups can orginate even from rwsem before |
| 380 | * up_read() however userfaults will wait either for a |
| 381 | * targeted wakeup on the specific uwq waitqueue from |
| 382 | * wake_userfault() or for signals or for uffd |
| 383 | * release. |
| 384 | */ |
| 385 | while (!READ_ONCE(uwq.waken)) { |
| 386 | /* |
| 387 | * This needs the full smp_store_mb() |
| 388 | * guarantee as the state write must be |
| 389 | * visible to other CPUs before reading |
| 390 | * uwq.waken from other CPUs. |
| 391 | */ |
| 392 | set_current_state(blocking_state); |
| 393 | if (READ_ONCE(uwq.waken) || |
| 394 | READ_ONCE(ctx->released) || |
| 395 | (return_to_userland ? signal_pending(current) : |
| 396 | fatal_signal_pending(current))) |
| 397 | break; |
| 398 | schedule(); |
| 399 | } |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 400 | } |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 401 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 402 | __set_current_state(TASK_RUNNING); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 403 | |
Andrea Arcangeli | dfa37dc | 2015-09-04 15:47:18 -0700 | [diff] [blame] | 404 | if (return_to_userland) { |
| 405 | if (signal_pending(current) && |
| 406 | !fatal_signal_pending(current)) { |
| 407 | /* |
| 408 | * If we got a SIGSTOP or SIGCONT and this is |
| 409 | * a normal userland page fault, just let |
| 410 | * userland return so the signal will be |
| 411 | * handled and gdb debugging works. The page |
| 412 | * fault code immediately after we return from |
| 413 | * this function is going to release the |
| 414 | * mmap_sem and it's not depending on it |
| 415 | * (unlike gup would if we were not to return |
| 416 | * VM_FAULT_RETRY). |
| 417 | * |
| 418 | * If a fatal signal is pending we still take |
| 419 | * the streamlined VM_FAULT_RETRY failure path |
| 420 | * and there's no need to retake the mmap_sem |
| 421 | * in such case. |
| 422 | */ |
| 423 | down_read(&mm->mmap_sem); |
| 424 | ret = 0; |
| 425 | } |
| 426 | } |
| 427 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 428 | /* |
| 429 | * Here we race with the list_del; list_add in |
| 430 | * userfaultfd_ctx_read(), however because we don't ever run |
| 431 | * list_del_init() to refile across the two lists, the prev |
| 432 | * and next pointers will never point to self. list_add also |
| 433 | * would never let any of the two pointers to point to |
| 434 | * self. So list_empty_careful won't risk to see both pointers |
| 435 | * pointing to self at any time during the list refile. The |
| 436 | * only case where list_del_init() is called is the full |
| 437 | * removal in the wake function and there we don't re-list_add |
| 438 | * and it's fine not to block on the spinlock. The uwq on this |
| 439 | * kernel stack can be released after the list_del_init. |
| 440 | */ |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 441 | if (!list_empty_careful(&uwq.wq.task_list)) { |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 442 | spin_lock(&ctx->fault_pending_wqh.lock); |
| 443 | /* |
| 444 | * No need of list_del_init(), the uwq on the stack |
| 445 | * will be freed shortly anyway. |
| 446 | */ |
| 447 | list_del(&uwq.wq.task_list); |
| 448 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 449 | } |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 450 | |
| 451 | /* |
| 452 | * ctx may go away after this if the userfault pseudo fd is |
| 453 | * already released. |
| 454 | */ |
| 455 | userfaultfd_ctx_put(ctx); |
| 456 | |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 457 | out: |
| 458 | return ret; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 459 | } |
| 460 | |
| 461 | static int userfaultfd_release(struct inode *inode, struct file *file) |
| 462 | { |
| 463 | struct userfaultfd_ctx *ctx = file->private_data; |
| 464 | struct mm_struct *mm = ctx->mm; |
| 465 | struct vm_area_struct *vma, *prev; |
| 466 | /* len == 0 means wake all */ |
| 467 | struct userfaultfd_wake_range range = { .len = 0, }; |
| 468 | unsigned long new_flags; |
| 469 | |
| 470 | ACCESS_ONCE(ctx->released) = true; |
| 471 | |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 472 | if (!mmget_not_zero(mm)) |
| 473 | goto wakeup; |
| 474 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 475 | /* |
| 476 | * Flush page faults out of all CPUs. NOTE: all page faults |
| 477 | * must be retried without returning VM_FAULT_SIGBUS if |
| 478 | * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx |
| 479 | * changes while handle_userfault released the mmap_sem. So |
| 480 | * it's critical that released is set to true (above), before |
| 481 | * taking the mmap_sem for writing. |
| 482 | */ |
| 483 | down_write(&mm->mmap_sem); |
| 484 | prev = NULL; |
| 485 | for (vma = mm->mmap; vma; vma = vma->vm_next) { |
| 486 | cond_resched(); |
| 487 | BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^ |
| 488 | !!(vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); |
| 489 | if (vma->vm_userfaultfd_ctx.ctx != ctx) { |
| 490 | prev = vma; |
| 491 | continue; |
| 492 | } |
| 493 | new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP); |
| 494 | prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end, |
| 495 | new_flags, vma->anon_vma, |
| 496 | vma->vm_file, vma->vm_pgoff, |
| 497 | vma_policy(vma), |
| 498 | NULL_VM_UFFD_CTX); |
| 499 | if (prev) |
| 500 | vma = prev; |
| 501 | else |
| 502 | prev = vma; |
| 503 | vma->vm_flags = new_flags; |
| 504 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; |
| 505 | } |
| 506 | up_write(&mm->mmap_sem); |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 507 | mmput(mm); |
| 508 | wakeup: |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 509 | /* |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 510 | * After no new page faults can wait on this fault_*wqh, flush |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 511 | * the last page faults that may have been already waiting on |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 512 | * the fault_*wqh. |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 513 | */ |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 514 | spin_lock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | ac5be6b | 2015-09-22 14:58:49 -0700 | [diff] [blame] | 515 | __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range); |
| 516 | __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, &range); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 517 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 518 | |
| 519 | wake_up_poll(&ctx->fd_wqh, POLLHUP); |
| 520 | userfaultfd_ctx_put(ctx); |
| 521 | return 0; |
| 522 | } |
| 523 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 524 | /* fault_pending_wqh.lock must be hold by the caller */ |
| 525 | static inline struct userfaultfd_wait_queue *find_userfault( |
| 526 | struct userfaultfd_ctx *ctx) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 527 | { |
| 528 | wait_queue_t *wq; |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 529 | struct userfaultfd_wait_queue *uwq; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 530 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 531 | VM_BUG_ON(!spin_is_locked(&ctx->fault_pending_wqh.lock)); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 532 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 533 | uwq = NULL; |
| 534 | if (!waitqueue_active(&ctx->fault_pending_wqh)) |
| 535 | goto out; |
| 536 | /* walk in reverse to provide FIFO behavior to read userfaults */ |
| 537 | wq = list_last_entry(&ctx->fault_pending_wqh.task_list, |
| 538 | typeof(*wq), task_list); |
| 539 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
| 540 | out: |
| 541 | return uwq; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 542 | } |
| 543 | |
| 544 | static unsigned int userfaultfd_poll(struct file *file, poll_table *wait) |
| 545 | { |
| 546 | struct userfaultfd_ctx *ctx = file->private_data; |
| 547 | unsigned int ret; |
| 548 | |
| 549 | poll_wait(file, &ctx->fd_wqh, wait); |
| 550 | |
| 551 | switch (ctx->state) { |
| 552 | case UFFD_STATE_WAIT_API: |
| 553 | return POLLERR; |
| 554 | case UFFD_STATE_RUNNING: |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 555 | /* |
| 556 | * poll() never guarantees that read won't block. |
| 557 | * userfaults can be waken before they're read(). |
| 558 | */ |
| 559 | if (unlikely(!(file->f_flags & O_NONBLOCK))) |
| 560 | return POLLERR; |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 561 | /* |
| 562 | * lockless access to see if there are pending faults |
| 563 | * __pollwait last action is the add_wait_queue but |
| 564 | * the spin_unlock would allow the waitqueue_active to |
| 565 | * pass above the actual list_add inside |
| 566 | * add_wait_queue critical section. So use a full |
| 567 | * memory barrier to serialize the list_add write of |
| 568 | * add_wait_queue() with the waitqueue_active read |
| 569 | * below. |
| 570 | */ |
| 571 | ret = 0; |
| 572 | smp_mb(); |
| 573 | if (waitqueue_active(&ctx->fault_pending_wqh)) |
| 574 | ret = POLLIN; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 575 | return ret; |
| 576 | default: |
| 577 | BUG(); |
| 578 | } |
| 579 | } |
| 580 | |
| 581 | static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 582 | struct uffd_msg *msg) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 583 | { |
| 584 | ssize_t ret; |
| 585 | DECLARE_WAITQUEUE(wait, current); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 586 | struct userfaultfd_wait_queue *uwq; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 587 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 588 | /* always take the fd_wqh lock before the fault_pending_wqh lock */ |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 589 | spin_lock(&ctx->fd_wqh.lock); |
| 590 | __add_wait_queue(&ctx->fd_wqh, &wait); |
| 591 | for (;;) { |
| 592 | set_current_state(TASK_INTERRUPTIBLE); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 593 | spin_lock(&ctx->fault_pending_wqh.lock); |
| 594 | uwq = find_userfault(ctx); |
| 595 | if (uwq) { |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 596 | /* |
Andrea Arcangeli | 2c5b7e1 | 2015-09-04 15:47:23 -0700 | [diff] [blame] | 597 | * Use a seqcount to repeat the lockless check |
| 598 | * in wake_userfault() to avoid missing |
| 599 | * wakeups because during the refile both |
| 600 | * waitqueue could become empty if this is the |
| 601 | * only userfault. |
| 602 | */ |
| 603 | write_seqcount_begin(&ctx->refile_seq); |
| 604 | |
| 605 | /* |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 606 | * The fault_pending_wqh.lock prevents the uwq |
| 607 | * to disappear from under us. |
| 608 | * |
| 609 | * Refile this userfault from |
| 610 | * fault_pending_wqh to fault_wqh, it's not |
| 611 | * pending anymore after we read it. |
| 612 | * |
| 613 | * Use list_del() by hand (as |
| 614 | * userfaultfd_wake_function also uses |
| 615 | * list_del_init() by hand) to be sure nobody |
| 616 | * changes __remove_wait_queue() to use |
| 617 | * list_del_init() in turn breaking the |
| 618 | * !list_empty_careful() check in |
| 619 | * handle_userfault(). The uwq->wq.task_list |
| 620 | * must never be empty at any time during the |
| 621 | * refile, or the waitqueue could disappear |
| 622 | * from under us. The "wait_queue_head_t" |
| 623 | * parameter of __remove_wait_queue() is unused |
| 624 | * anyway. |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 625 | */ |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 626 | list_del(&uwq->wq.task_list); |
| 627 | __add_wait_queue(&ctx->fault_wqh, &uwq->wq); |
| 628 | |
Andrea Arcangeli | 2c5b7e1 | 2015-09-04 15:47:23 -0700 | [diff] [blame] | 629 | write_seqcount_end(&ctx->refile_seq); |
| 630 | |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 631 | /* careful to always initialize msg if ret == 0 */ |
| 632 | *msg = uwq->msg; |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 633 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 634 | ret = 0; |
| 635 | break; |
| 636 | } |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 637 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 638 | if (signal_pending(current)) { |
| 639 | ret = -ERESTARTSYS; |
| 640 | break; |
| 641 | } |
| 642 | if (no_wait) { |
| 643 | ret = -EAGAIN; |
| 644 | break; |
| 645 | } |
| 646 | spin_unlock(&ctx->fd_wqh.lock); |
| 647 | schedule(); |
| 648 | spin_lock(&ctx->fd_wqh.lock); |
| 649 | } |
| 650 | __remove_wait_queue(&ctx->fd_wqh, &wait); |
| 651 | __set_current_state(TASK_RUNNING); |
| 652 | spin_unlock(&ctx->fd_wqh.lock); |
| 653 | |
| 654 | return ret; |
| 655 | } |
| 656 | |
| 657 | static ssize_t userfaultfd_read(struct file *file, char __user *buf, |
| 658 | size_t count, loff_t *ppos) |
| 659 | { |
| 660 | struct userfaultfd_ctx *ctx = file->private_data; |
| 661 | ssize_t _ret, ret = 0; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 662 | struct uffd_msg msg; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 663 | int no_wait = file->f_flags & O_NONBLOCK; |
| 664 | |
| 665 | if (ctx->state == UFFD_STATE_WAIT_API) |
| 666 | return -EINVAL; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 667 | |
| 668 | for (;;) { |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 669 | if (count < sizeof(msg)) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 670 | return ret ? ret : -EINVAL; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 671 | _ret = userfaultfd_ctx_read(ctx, no_wait, &msg); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 672 | if (_ret < 0) |
| 673 | return ret ? ret : _ret; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 674 | if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg))) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 675 | return ret ? ret : -EFAULT; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 676 | ret += sizeof(msg); |
| 677 | buf += sizeof(msg); |
| 678 | count -= sizeof(msg); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 679 | /* |
| 680 | * Allow to read more than one fault at time but only |
| 681 | * block if waiting for the very first one. |
| 682 | */ |
| 683 | no_wait = O_NONBLOCK; |
| 684 | } |
| 685 | } |
| 686 | |
| 687 | static void __wake_userfault(struct userfaultfd_ctx *ctx, |
| 688 | struct userfaultfd_wake_range *range) |
| 689 | { |
| 690 | unsigned long start, end; |
| 691 | |
| 692 | start = range->start; |
| 693 | end = range->start + range->len; |
| 694 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 695 | spin_lock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 696 | /* wake all in the range and autoremove */ |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 697 | if (waitqueue_active(&ctx->fault_pending_wqh)) |
Andrea Arcangeli | ac5be6b | 2015-09-22 14:58:49 -0700 | [diff] [blame] | 698 | __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 699 | range); |
| 700 | if (waitqueue_active(&ctx->fault_wqh)) |
Andrea Arcangeli | ac5be6b | 2015-09-22 14:58:49 -0700 | [diff] [blame] | 701 | __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, range); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 702 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 703 | } |
| 704 | |
| 705 | static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx, |
| 706 | struct userfaultfd_wake_range *range) |
| 707 | { |
Andrea Arcangeli | 2c5b7e1 | 2015-09-04 15:47:23 -0700 | [diff] [blame] | 708 | unsigned seq; |
| 709 | bool need_wakeup; |
| 710 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 711 | /* |
| 712 | * To be sure waitqueue_active() is not reordered by the CPU |
| 713 | * before the pagetable update, use an explicit SMP memory |
| 714 | * barrier here. PT lock release or up_read(mmap_sem) still |
| 715 | * have release semantics that can allow the |
| 716 | * waitqueue_active() to be reordered before the pte update. |
| 717 | */ |
| 718 | smp_mb(); |
| 719 | |
| 720 | /* |
| 721 | * Use waitqueue_active because it's very frequent to |
| 722 | * change the address space atomically even if there are no |
| 723 | * userfaults yet. So we take the spinlock only when we're |
| 724 | * sure we've userfaults to wake. |
| 725 | */ |
Andrea Arcangeli | 2c5b7e1 | 2015-09-04 15:47:23 -0700 | [diff] [blame] | 726 | do { |
| 727 | seq = read_seqcount_begin(&ctx->refile_seq); |
| 728 | need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) || |
| 729 | waitqueue_active(&ctx->fault_wqh); |
| 730 | cond_resched(); |
| 731 | } while (read_seqcount_retry(&ctx->refile_seq, seq)); |
| 732 | if (need_wakeup) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 733 | __wake_userfault(ctx, range); |
| 734 | } |
| 735 | |
| 736 | static __always_inline int validate_range(struct mm_struct *mm, |
| 737 | __u64 start, __u64 len) |
| 738 | { |
| 739 | __u64 task_size = mm->task_size; |
| 740 | |
| 741 | if (start & ~PAGE_MASK) |
| 742 | return -EINVAL; |
| 743 | if (len & ~PAGE_MASK) |
| 744 | return -EINVAL; |
| 745 | if (!len) |
| 746 | return -EINVAL; |
| 747 | if (start < mmap_min_addr) |
| 748 | return -EINVAL; |
| 749 | if (start >= task_size) |
| 750 | return -EINVAL; |
| 751 | if (len > task_size - start) |
| 752 | return -EINVAL; |
| 753 | return 0; |
| 754 | } |
| 755 | |
| 756 | static int userfaultfd_register(struct userfaultfd_ctx *ctx, |
| 757 | unsigned long arg) |
| 758 | { |
| 759 | struct mm_struct *mm = ctx->mm; |
| 760 | struct vm_area_struct *vma, *prev, *cur; |
| 761 | int ret; |
| 762 | struct uffdio_register uffdio_register; |
| 763 | struct uffdio_register __user *user_uffdio_register; |
| 764 | unsigned long vm_flags, new_flags; |
| 765 | bool found; |
| 766 | unsigned long start, end, vma_end; |
| 767 | |
| 768 | user_uffdio_register = (struct uffdio_register __user *) arg; |
| 769 | |
| 770 | ret = -EFAULT; |
| 771 | if (copy_from_user(&uffdio_register, user_uffdio_register, |
| 772 | sizeof(uffdio_register)-sizeof(__u64))) |
| 773 | goto out; |
| 774 | |
| 775 | ret = -EINVAL; |
| 776 | if (!uffdio_register.mode) |
| 777 | goto out; |
| 778 | if (uffdio_register.mode & ~(UFFDIO_REGISTER_MODE_MISSING| |
| 779 | UFFDIO_REGISTER_MODE_WP)) |
| 780 | goto out; |
| 781 | vm_flags = 0; |
| 782 | if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING) |
| 783 | vm_flags |= VM_UFFD_MISSING; |
| 784 | if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) { |
| 785 | vm_flags |= VM_UFFD_WP; |
| 786 | /* |
| 787 | * FIXME: remove the below error constraint by |
| 788 | * implementing the wprotect tracking mode. |
| 789 | */ |
| 790 | ret = -EINVAL; |
| 791 | goto out; |
| 792 | } |
| 793 | |
| 794 | ret = validate_range(mm, uffdio_register.range.start, |
| 795 | uffdio_register.range.len); |
| 796 | if (ret) |
| 797 | goto out; |
| 798 | |
| 799 | start = uffdio_register.range.start; |
| 800 | end = start + uffdio_register.range.len; |
| 801 | |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 802 | ret = -ENOMEM; |
| 803 | if (!mmget_not_zero(mm)) |
| 804 | goto out; |
| 805 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 806 | down_write(&mm->mmap_sem); |
| 807 | vma = find_vma_prev(mm, start, &prev); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 808 | if (!vma) |
| 809 | goto out_unlock; |
| 810 | |
| 811 | /* check that there's at least one vma in the range */ |
| 812 | ret = -EINVAL; |
| 813 | if (vma->vm_start >= end) |
| 814 | goto out_unlock; |
| 815 | |
| 816 | /* |
| 817 | * Search for not compatible vmas. |
| 818 | * |
| 819 | * FIXME: this shall be relaxed later so that it doesn't fail |
| 820 | * on tmpfs backed vmas (in addition to the current allowance |
| 821 | * on anonymous vmas). |
| 822 | */ |
| 823 | found = false; |
| 824 | for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) { |
| 825 | cond_resched(); |
| 826 | |
| 827 | BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ |
| 828 | !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); |
| 829 | |
| 830 | /* check not compatible vmas */ |
| 831 | ret = -EINVAL; |
| 832 | if (cur->vm_ops) |
| 833 | goto out_unlock; |
| 834 | |
| 835 | /* |
| 836 | * Check that this vma isn't already owned by a |
| 837 | * different userfaultfd. We can't allow more than one |
| 838 | * userfaultfd to own a single vma simultaneously or we |
| 839 | * wouldn't know which one to deliver the userfaults to. |
| 840 | */ |
| 841 | ret = -EBUSY; |
| 842 | if (cur->vm_userfaultfd_ctx.ctx && |
| 843 | cur->vm_userfaultfd_ctx.ctx != ctx) |
| 844 | goto out_unlock; |
| 845 | |
| 846 | found = true; |
| 847 | } |
| 848 | BUG_ON(!found); |
| 849 | |
| 850 | if (vma->vm_start < start) |
| 851 | prev = vma; |
| 852 | |
| 853 | ret = 0; |
| 854 | do { |
| 855 | cond_resched(); |
| 856 | |
| 857 | BUG_ON(vma->vm_ops); |
| 858 | BUG_ON(vma->vm_userfaultfd_ctx.ctx && |
| 859 | vma->vm_userfaultfd_ctx.ctx != ctx); |
| 860 | |
| 861 | /* |
| 862 | * Nothing to do: this vma is already registered into this |
| 863 | * userfaultfd and with the right tracking mode too. |
| 864 | */ |
| 865 | if (vma->vm_userfaultfd_ctx.ctx == ctx && |
| 866 | (vma->vm_flags & vm_flags) == vm_flags) |
| 867 | goto skip; |
| 868 | |
| 869 | if (vma->vm_start > start) |
| 870 | start = vma->vm_start; |
| 871 | vma_end = min(end, vma->vm_end); |
| 872 | |
| 873 | new_flags = (vma->vm_flags & ~vm_flags) | vm_flags; |
| 874 | prev = vma_merge(mm, prev, start, vma_end, new_flags, |
| 875 | vma->anon_vma, vma->vm_file, vma->vm_pgoff, |
| 876 | vma_policy(vma), |
| 877 | ((struct vm_userfaultfd_ctx){ ctx })); |
| 878 | if (prev) { |
| 879 | vma = prev; |
| 880 | goto next; |
| 881 | } |
| 882 | if (vma->vm_start < start) { |
| 883 | ret = split_vma(mm, vma, start, 1); |
| 884 | if (ret) |
| 885 | break; |
| 886 | } |
| 887 | if (vma->vm_end > end) { |
| 888 | ret = split_vma(mm, vma, end, 0); |
| 889 | if (ret) |
| 890 | break; |
| 891 | } |
| 892 | next: |
| 893 | /* |
| 894 | * In the vma_merge() successful mprotect-like case 8: |
| 895 | * the next vma was merged into the current one and |
| 896 | * the current one has not been updated yet. |
| 897 | */ |
| 898 | vma->vm_flags = new_flags; |
| 899 | vma->vm_userfaultfd_ctx.ctx = ctx; |
| 900 | |
| 901 | skip: |
| 902 | prev = vma; |
| 903 | start = vma->vm_end; |
| 904 | vma = vma->vm_next; |
| 905 | } while (vma && vma->vm_start < end); |
| 906 | out_unlock: |
| 907 | up_write(&mm->mmap_sem); |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 908 | mmput(mm); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 909 | if (!ret) { |
| 910 | /* |
| 911 | * Now that we scanned all vmas we can already tell |
| 912 | * userland which ioctls methods are guaranteed to |
| 913 | * succeed on this range. |
| 914 | */ |
| 915 | if (put_user(UFFD_API_RANGE_IOCTLS, |
| 916 | &user_uffdio_register->ioctls)) |
| 917 | ret = -EFAULT; |
| 918 | } |
| 919 | out: |
| 920 | return ret; |
| 921 | } |
| 922 | |
| 923 | static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, |
| 924 | unsigned long arg) |
| 925 | { |
| 926 | struct mm_struct *mm = ctx->mm; |
| 927 | struct vm_area_struct *vma, *prev, *cur; |
| 928 | int ret; |
| 929 | struct uffdio_range uffdio_unregister; |
| 930 | unsigned long new_flags; |
| 931 | bool found; |
| 932 | unsigned long start, end, vma_end; |
| 933 | const void __user *buf = (void __user *)arg; |
| 934 | |
| 935 | ret = -EFAULT; |
| 936 | if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister))) |
| 937 | goto out; |
| 938 | |
| 939 | ret = validate_range(mm, uffdio_unregister.start, |
| 940 | uffdio_unregister.len); |
| 941 | if (ret) |
| 942 | goto out; |
| 943 | |
| 944 | start = uffdio_unregister.start; |
| 945 | end = start + uffdio_unregister.len; |
| 946 | |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 947 | ret = -ENOMEM; |
| 948 | if (!mmget_not_zero(mm)) |
| 949 | goto out; |
| 950 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 951 | down_write(&mm->mmap_sem); |
| 952 | vma = find_vma_prev(mm, start, &prev); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 953 | if (!vma) |
| 954 | goto out_unlock; |
| 955 | |
| 956 | /* check that there's at least one vma in the range */ |
| 957 | ret = -EINVAL; |
| 958 | if (vma->vm_start >= end) |
| 959 | goto out_unlock; |
| 960 | |
| 961 | /* |
| 962 | * Search for not compatible vmas. |
| 963 | * |
| 964 | * FIXME: this shall be relaxed later so that it doesn't fail |
| 965 | * on tmpfs backed vmas (in addition to the current allowance |
| 966 | * on anonymous vmas). |
| 967 | */ |
| 968 | found = false; |
| 969 | ret = -EINVAL; |
| 970 | for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) { |
| 971 | cond_resched(); |
| 972 | |
| 973 | BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ |
| 974 | !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); |
| 975 | |
| 976 | /* |
| 977 | * Check not compatible vmas, not strictly required |
| 978 | * here as not compatible vmas cannot have an |
| 979 | * userfaultfd_ctx registered on them, but this |
| 980 | * provides for more strict behavior to notice |
| 981 | * unregistration errors. |
| 982 | */ |
| 983 | if (cur->vm_ops) |
| 984 | goto out_unlock; |
| 985 | |
| 986 | found = true; |
| 987 | } |
| 988 | BUG_ON(!found); |
| 989 | |
| 990 | if (vma->vm_start < start) |
| 991 | prev = vma; |
| 992 | |
| 993 | ret = 0; |
| 994 | do { |
| 995 | cond_resched(); |
| 996 | |
| 997 | BUG_ON(vma->vm_ops); |
| 998 | |
| 999 | /* |
| 1000 | * Nothing to do: this vma is already registered into this |
| 1001 | * userfaultfd and with the right tracking mode too. |
| 1002 | */ |
| 1003 | if (!vma->vm_userfaultfd_ctx.ctx) |
| 1004 | goto skip; |
| 1005 | |
| 1006 | if (vma->vm_start > start) |
| 1007 | start = vma->vm_start; |
| 1008 | vma_end = min(end, vma->vm_end); |
| 1009 | |
| 1010 | new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP); |
| 1011 | prev = vma_merge(mm, prev, start, vma_end, new_flags, |
| 1012 | vma->anon_vma, vma->vm_file, vma->vm_pgoff, |
| 1013 | vma_policy(vma), |
| 1014 | NULL_VM_UFFD_CTX); |
| 1015 | if (prev) { |
| 1016 | vma = prev; |
| 1017 | goto next; |
| 1018 | } |
| 1019 | if (vma->vm_start < start) { |
| 1020 | ret = split_vma(mm, vma, start, 1); |
| 1021 | if (ret) |
| 1022 | break; |
| 1023 | } |
| 1024 | if (vma->vm_end > end) { |
| 1025 | ret = split_vma(mm, vma, end, 0); |
| 1026 | if (ret) |
| 1027 | break; |
| 1028 | } |
| 1029 | next: |
| 1030 | /* |
| 1031 | * In the vma_merge() successful mprotect-like case 8: |
| 1032 | * the next vma was merged into the current one and |
| 1033 | * the current one has not been updated yet. |
| 1034 | */ |
| 1035 | vma->vm_flags = new_flags; |
| 1036 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; |
| 1037 | |
| 1038 | skip: |
| 1039 | prev = vma; |
| 1040 | start = vma->vm_end; |
| 1041 | vma = vma->vm_next; |
| 1042 | } while (vma && vma->vm_start < end); |
| 1043 | out_unlock: |
| 1044 | up_write(&mm->mmap_sem); |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1045 | mmput(mm); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1046 | out: |
| 1047 | return ret; |
| 1048 | } |
| 1049 | |
| 1050 | /* |
Andrea Arcangeli | ba85c70 | 2015-09-04 15:46:41 -0700 | [diff] [blame] | 1051 | * userfaultfd_wake may be used in combination with the |
| 1052 | * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches. |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1053 | */ |
| 1054 | static int userfaultfd_wake(struct userfaultfd_ctx *ctx, |
| 1055 | unsigned long arg) |
| 1056 | { |
| 1057 | int ret; |
| 1058 | struct uffdio_range uffdio_wake; |
| 1059 | struct userfaultfd_wake_range range; |
| 1060 | const void __user *buf = (void __user *)arg; |
| 1061 | |
| 1062 | ret = -EFAULT; |
| 1063 | if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake))) |
| 1064 | goto out; |
| 1065 | |
| 1066 | ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len); |
| 1067 | if (ret) |
| 1068 | goto out; |
| 1069 | |
| 1070 | range.start = uffdio_wake.start; |
| 1071 | range.len = uffdio_wake.len; |
| 1072 | |
| 1073 | /* |
| 1074 | * len == 0 means wake all and we don't want to wake all here, |
| 1075 | * so check it again to be sure. |
| 1076 | */ |
| 1077 | VM_BUG_ON(!range.len); |
| 1078 | |
| 1079 | wake_userfault(ctx, &range); |
| 1080 | ret = 0; |
| 1081 | |
| 1082 | out: |
| 1083 | return ret; |
| 1084 | } |
| 1085 | |
Andrea Arcangeli | ad465ca | 2015-09-04 15:47:11 -0700 | [diff] [blame] | 1086 | static int userfaultfd_copy(struct userfaultfd_ctx *ctx, |
| 1087 | unsigned long arg) |
| 1088 | { |
| 1089 | __s64 ret; |
| 1090 | struct uffdio_copy uffdio_copy; |
| 1091 | struct uffdio_copy __user *user_uffdio_copy; |
| 1092 | struct userfaultfd_wake_range range; |
| 1093 | |
| 1094 | user_uffdio_copy = (struct uffdio_copy __user *) arg; |
| 1095 | |
| 1096 | ret = -EFAULT; |
| 1097 | if (copy_from_user(&uffdio_copy, user_uffdio_copy, |
| 1098 | /* don't copy "copy" last field */ |
| 1099 | sizeof(uffdio_copy)-sizeof(__s64))) |
| 1100 | goto out; |
| 1101 | |
| 1102 | ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len); |
| 1103 | if (ret) |
| 1104 | goto out; |
| 1105 | /* |
| 1106 | * double check for wraparound just in case. copy_from_user() |
| 1107 | * will later check uffdio_copy.src + uffdio_copy.len to fit |
| 1108 | * in the userland range. |
| 1109 | */ |
| 1110 | ret = -EINVAL; |
| 1111 | if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src) |
| 1112 | goto out; |
| 1113 | if (uffdio_copy.mode & ~UFFDIO_COPY_MODE_DONTWAKE) |
| 1114 | goto out; |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1115 | if (mmget_not_zero(ctx->mm)) { |
| 1116 | ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src, |
| 1117 | uffdio_copy.len); |
| 1118 | mmput(ctx->mm); |
| 1119 | } |
Andrea Arcangeli | ad465ca | 2015-09-04 15:47:11 -0700 | [diff] [blame] | 1120 | if (unlikely(put_user(ret, &user_uffdio_copy->copy))) |
| 1121 | return -EFAULT; |
| 1122 | if (ret < 0) |
| 1123 | goto out; |
| 1124 | BUG_ON(!ret); |
| 1125 | /* len == 0 would wake all */ |
| 1126 | range.len = ret; |
| 1127 | if (!(uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE)) { |
| 1128 | range.start = uffdio_copy.dst; |
| 1129 | wake_userfault(ctx, &range); |
| 1130 | } |
| 1131 | ret = range.len == uffdio_copy.len ? 0 : -EAGAIN; |
| 1132 | out: |
| 1133 | return ret; |
| 1134 | } |
| 1135 | |
| 1136 | static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx, |
| 1137 | unsigned long arg) |
| 1138 | { |
| 1139 | __s64 ret; |
| 1140 | struct uffdio_zeropage uffdio_zeropage; |
| 1141 | struct uffdio_zeropage __user *user_uffdio_zeropage; |
| 1142 | struct userfaultfd_wake_range range; |
| 1143 | |
| 1144 | user_uffdio_zeropage = (struct uffdio_zeropage __user *) arg; |
| 1145 | |
| 1146 | ret = -EFAULT; |
| 1147 | if (copy_from_user(&uffdio_zeropage, user_uffdio_zeropage, |
| 1148 | /* don't copy "zeropage" last field */ |
| 1149 | sizeof(uffdio_zeropage)-sizeof(__s64))) |
| 1150 | goto out; |
| 1151 | |
| 1152 | ret = validate_range(ctx->mm, uffdio_zeropage.range.start, |
| 1153 | uffdio_zeropage.range.len); |
| 1154 | if (ret) |
| 1155 | goto out; |
| 1156 | ret = -EINVAL; |
| 1157 | if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE) |
| 1158 | goto out; |
| 1159 | |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1160 | if (mmget_not_zero(ctx->mm)) { |
| 1161 | ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start, |
| 1162 | uffdio_zeropage.range.len); |
| 1163 | mmput(ctx->mm); |
| 1164 | } |
Andrea Arcangeli | ad465ca | 2015-09-04 15:47:11 -0700 | [diff] [blame] | 1165 | if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage))) |
| 1166 | return -EFAULT; |
| 1167 | if (ret < 0) |
| 1168 | goto out; |
| 1169 | /* len == 0 would wake all */ |
| 1170 | BUG_ON(!ret); |
| 1171 | range.len = ret; |
| 1172 | if (!(uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_DONTWAKE)) { |
| 1173 | range.start = uffdio_zeropage.range.start; |
| 1174 | wake_userfault(ctx, &range); |
| 1175 | } |
| 1176 | ret = range.len == uffdio_zeropage.range.len ? 0 : -EAGAIN; |
| 1177 | out: |
| 1178 | return ret; |
| 1179 | } |
| 1180 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1181 | /* |
| 1182 | * userland asks for a certain API version and we return which bits |
| 1183 | * and ioctl commands are implemented in this kernel for such API |
| 1184 | * version or -EINVAL if unknown. |
| 1185 | */ |
| 1186 | static int userfaultfd_api(struct userfaultfd_ctx *ctx, |
| 1187 | unsigned long arg) |
| 1188 | { |
| 1189 | struct uffdio_api uffdio_api; |
| 1190 | void __user *buf = (void __user *)arg; |
| 1191 | int ret; |
| 1192 | |
| 1193 | ret = -EINVAL; |
| 1194 | if (ctx->state != UFFD_STATE_WAIT_API) |
| 1195 | goto out; |
| 1196 | ret = -EFAULT; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 1197 | if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api))) |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1198 | goto out; |
Andrea Arcangeli | a9b85f9 | 2015-09-04 15:46:37 -0700 | [diff] [blame] | 1199 | if (uffdio_api.api != UFFD_API || uffdio_api.features) { |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1200 | memset(&uffdio_api, 0, sizeof(uffdio_api)); |
| 1201 | if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) |
| 1202 | goto out; |
| 1203 | ret = -EINVAL; |
| 1204 | goto out; |
| 1205 | } |
Pavel Emelyanov | 3f602d2 | 2015-09-04 15:46:34 -0700 | [diff] [blame] | 1206 | uffdio_api.features = UFFD_API_FEATURES; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1207 | uffdio_api.ioctls = UFFD_API_IOCTLS; |
| 1208 | ret = -EFAULT; |
| 1209 | if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) |
| 1210 | goto out; |
| 1211 | ctx->state = UFFD_STATE_RUNNING; |
| 1212 | ret = 0; |
| 1213 | out: |
| 1214 | return ret; |
| 1215 | } |
| 1216 | |
| 1217 | static long userfaultfd_ioctl(struct file *file, unsigned cmd, |
| 1218 | unsigned long arg) |
| 1219 | { |
| 1220 | int ret = -EINVAL; |
| 1221 | struct userfaultfd_ctx *ctx = file->private_data; |
| 1222 | |
Andrea Arcangeli | e6485a4 | 2015-09-04 15:47:15 -0700 | [diff] [blame] | 1223 | if (cmd != UFFDIO_API && ctx->state == UFFD_STATE_WAIT_API) |
| 1224 | return -EINVAL; |
| 1225 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1226 | switch(cmd) { |
| 1227 | case UFFDIO_API: |
| 1228 | ret = userfaultfd_api(ctx, arg); |
| 1229 | break; |
| 1230 | case UFFDIO_REGISTER: |
| 1231 | ret = userfaultfd_register(ctx, arg); |
| 1232 | break; |
| 1233 | case UFFDIO_UNREGISTER: |
| 1234 | ret = userfaultfd_unregister(ctx, arg); |
| 1235 | break; |
| 1236 | case UFFDIO_WAKE: |
| 1237 | ret = userfaultfd_wake(ctx, arg); |
| 1238 | break; |
Andrea Arcangeli | ad465ca | 2015-09-04 15:47:11 -0700 | [diff] [blame] | 1239 | case UFFDIO_COPY: |
| 1240 | ret = userfaultfd_copy(ctx, arg); |
| 1241 | break; |
| 1242 | case UFFDIO_ZEROPAGE: |
| 1243 | ret = userfaultfd_zeropage(ctx, arg); |
| 1244 | break; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1245 | } |
| 1246 | return ret; |
| 1247 | } |
| 1248 | |
| 1249 | #ifdef CONFIG_PROC_FS |
| 1250 | static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f) |
| 1251 | { |
| 1252 | struct userfaultfd_ctx *ctx = f->private_data; |
| 1253 | wait_queue_t *wq; |
| 1254 | struct userfaultfd_wait_queue *uwq; |
| 1255 | unsigned long pending = 0, total = 0; |
| 1256 | |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 1257 | spin_lock(&ctx->fault_pending_wqh.lock); |
| 1258 | list_for_each_entry(wq, &ctx->fault_pending_wqh.task_list, task_list) { |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1259 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 1260 | pending++; |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1261 | total++; |
| 1262 | } |
Andrea Arcangeli | 15b726e | 2015-09-04 15:46:44 -0700 | [diff] [blame] | 1263 | list_for_each_entry(wq, &ctx->fault_wqh.task_list, task_list) { |
| 1264 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
| 1265 | total++; |
| 1266 | } |
| 1267 | spin_unlock(&ctx->fault_pending_wqh.lock); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1268 | |
| 1269 | /* |
| 1270 | * If more protocols will be added, there will be all shown |
| 1271 | * separated by a space. Like this: |
| 1272 | * protocols: aa:... bb:... |
| 1273 | */ |
| 1274 | seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n", |
Pavel Emelyanov | 3f602d2 | 2015-09-04 15:46:34 -0700 | [diff] [blame] | 1275 | pending, total, UFFD_API, UFFD_API_FEATURES, |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1276 | UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS); |
| 1277 | } |
| 1278 | #endif |
| 1279 | |
| 1280 | static const struct file_operations userfaultfd_fops = { |
| 1281 | #ifdef CONFIG_PROC_FS |
| 1282 | .show_fdinfo = userfaultfd_show_fdinfo, |
| 1283 | #endif |
| 1284 | .release = userfaultfd_release, |
| 1285 | .poll = userfaultfd_poll, |
| 1286 | .read = userfaultfd_read, |
| 1287 | .unlocked_ioctl = userfaultfd_ioctl, |
| 1288 | .compat_ioctl = userfaultfd_ioctl, |
| 1289 | .llseek = noop_llseek, |
| 1290 | }; |
| 1291 | |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 1292 | static void init_once_userfaultfd_ctx(void *mem) |
| 1293 | { |
| 1294 | struct userfaultfd_ctx *ctx = (struct userfaultfd_ctx *) mem; |
| 1295 | |
| 1296 | init_waitqueue_head(&ctx->fault_pending_wqh); |
| 1297 | init_waitqueue_head(&ctx->fault_wqh); |
| 1298 | init_waitqueue_head(&ctx->fd_wqh); |
Andrea Arcangeli | 2c5b7e1 | 2015-09-04 15:47:23 -0700 | [diff] [blame] | 1299 | seqcount_init(&ctx->refile_seq); |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 1300 | } |
| 1301 | |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1302 | /** |
| 1303 | * userfaultfd_file_create - Creates an userfaultfd file pointer. |
| 1304 | * @flags: Flags for the userfaultfd file. |
| 1305 | * |
| 1306 | * This function creates an userfaultfd file pointer, w/out installing |
| 1307 | * it into the fd table. This is useful when the userfaultfd file is |
| 1308 | * used during the initialization of data structures that require |
| 1309 | * extra setup after the userfaultfd creation. So the userfaultfd |
| 1310 | * creation is split into the file pointer creation phase, and the |
| 1311 | * file descriptor installation phase. In this way races with |
| 1312 | * userspace closing the newly installed file descriptor can be |
| 1313 | * avoided. Returns an userfaultfd file pointer, or a proper error |
| 1314 | * pointer. |
| 1315 | */ |
| 1316 | static struct file *userfaultfd_file_create(int flags) |
| 1317 | { |
| 1318 | struct file *file; |
| 1319 | struct userfaultfd_ctx *ctx; |
| 1320 | |
| 1321 | BUG_ON(!current->mm); |
| 1322 | |
| 1323 | /* Check the UFFD_* constants for consistency. */ |
| 1324 | BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC); |
| 1325 | BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK); |
| 1326 | |
| 1327 | file = ERR_PTR(-EINVAL); |
| 1328 | if (flags & ~UFFD_SHARED_FCNTL_FLAGS) |
| 1329 | goto out; |
| 1330 | |
| 1331 | file = ERR_PTR(-ENOMEM); |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 1332 | ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1333 | if (!ctx) |
| 1334 | goto out; |
| 1335 | |
| 1336 | atomic_set(&ctx->refcount, 1); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1337 | ctx->flags = flags; |
| 1338 | ctx->state = UFFD_STATE_WAIT_API; |
| 1339 | ctx->released = false; |
| 1340 | ctx->mm = current->mm; |
| 1341 | /* prevent the mm struct to be freed */ |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1342 | atomic_inc(&ctx->mm->mm_count); |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1343 | |
| 1344 | file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, ctx, |
| 1345 | O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS)); |
Eric Biggers | c03e946 | 2015-09-17 16:01:54 -0700 | [diff] [blame] | 1346 | if (IS_ERR(file)) { |
Oleg Nesterov | d2005e3 | 2016-05-20 16:58:36 -0700 | [diff] [blame] | 1347 | mmdrop(ctx->mm); |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 1348 | kmem_cache_free(userfaultfd_ctx_cachep, ctx); |
Eric Biggers | c03e946 | 2015-09-17 16:01:54 -0700 | [diff] [blame] | 1349 | } |
Andrea Arcangeli | 86039bd | 2015-09-04 15:46:31 -0700 | [diff] [blame] | 1350 | out: |
| 1351 | return file; |
| 1352 | } |
| 1353 | |
| 1354 | SYSCALL_DEFINE1(userfaultfd, int, flags) |
| 1355 | { |
| 1356 | int fd, error; |
| 1357 | struct file *file; |
| 1358 | |
| 1359 | error = get_unused_fd_flags(flags & UFFD_SHARED_FCNTL_FLAGS); |
| 1360 | if (error < 0) |
| 1361 | return error; |
| 1362 | fd = error; |
| 1363 | |
| 1364 | file = userfaultfd_file_create(flags); |
| 1365 | if (IS_ERR(file)) { |
| 1366 | error = PTR_ERR(file); |
| 1367 | goto err_put_unused_fd; |
| 1368 | } |
| 1369 | fd_install(fd, file); |
| 1370 | |
| 1371 | return fd; |
| 1372 | |
| 1373 | err_put_unused_fd: |
| 1374 | put_unused_fd(fd); |
| 1375 | |
| 1376 | return error; |
| 1377 | } |
Andrea Arcangeli | 3004ec9 | 2015-09-04 15:46:48 -0700 | [diff] [blame] | 1378 | |
| 1379 | static int __init userfaultfd_init(void) |
| 1380 | { |
| 1381 | userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache", |
| 1382 | sizeof(struct userfaultfd_ctx), |
| 1383 | 0, |
| 1384 | SLAB_HWCACHE_ALIGN|SLAB_PANIC, |
| 1385 | init_once_userfaultfd_ctx); |
| 1386 | return 0; |
| 1387 | } |
| 1388 | __initcall(userfaultfd_init); |